Introduction: Melatonin receptors belong to the large class of G-protein coupled membrane receptors. Recently published data speak in favour of a coupling of MT1 melatonin receptors on G-proteins of the Gi, as well as of the Gq class. Activation of the former triggers a cascade which leads to a reduction of adenylate cyclase activity and subsequently to a reduction of intracellular cAMP concentrations. Through alternative coupling of the MT1 to Gq proteins the release of the second messenger IP3 is induced, leading, consecutively, to an increase in intracellular calcium concentration. Activation of MT2 receptors, however, results in a reduction of the guanylate cyclase activity and consecutively of cGMP concentrations due to coupling to inhibitory Gi-proteins. In the present study, these melatonin-evoked signaling pathways were analysed in a rat insulinoma b-cell line (INS1).

Introduction: There is a well-documented link between melatonin and insulin. Morphological, molecular and functional investigations have shown that the pineal hormone melatonin (MT) reduces insulin secretion in vitro as well as in control and type 2 diabetic rats. The effects were mediated by specific, high-affinity, pertussis-toxin-sensitive, G-protein-coupled MT1- as well as MT2-membrane receptors, which were detected in the pancreatic tissue of rats and humans, in the islets of rats and in a rat insulinoma b-cell line (INS1). Addressing both the Gi-adenylylcyclase-cAMP and Gi-guanylylcyclase-cGMP pathways, MT decreases insulin secretion, whereas, activation of the Gq-phospholipase C-IP3 pathway, MT increases insulin secretion.

Introduction: Numerous studies recently provided evidence for an interrelationship between melatonin and insulin. Perifusion experiments with rat islets of Langerhans demonstrated, that the insulin secretion exhibits a circadian rhythm, which could be phase-shifted after melatonin application. Furthermore, in vitro and animal investigations established, that melatonin inhibits the insulin secretion. Aim of the present study was the analysis of melatonin receptors as possible mediators of melatonin action in pancreatic tissue of rats and humans as well as the characterization of melatonin receptors of non diabetic and type 2 diabetic patients.

Introduction: Melatonin receptors (MT1 and MT2) in pancreatic β-cells and both the adenylyl-cyclase-cAMP and guanylyl-cyclase-cGMP pathways are prerequisites for the well-known suppression of insulin secretion by melatonin. We found reduced melatonin plasma levels in type 2 diabetic patients as well as in type 2 diabetic Goto Kakizaki (GK) rats, a model of non-insulin-dependent diabetes mellitus (NIDDM). Previous studies have investigated the differences in glucose, insulin and melatonin levels in type 2 diabetic rats and humans. Moreover, expression of pineal insulin receptor (InsR)- and arylalkylamine-N-acetyl-tranferase (AANAT)-mRNA has been monitored in type 2 diabetic rats. The present study investigated plasma glucose, insulin and melatonin, as well as the transcripts of InsR, AANAT, hydroxyindole-O-methyltransferase (HIOMT) and the ß1-adrenoceptor of pineal glands, using real-time RT-PCR in type 1 diabetic streptozotocin (STZ)- and insulin-dependent diabetes mellitus (IDDM) rats to compare these parameters with those of type 2 diabetic animals and patients.

In vitro- und tierexperimentelle Untersuchungen konnten eindeutig belegen, dass das epiphysäre Indolamin Melatonin die Insulinsekretion Rezeptor-mediiert senkt. Bisher gab es ausschließlich eindeutige Belege für die Existenz von MT1-Melatoninrezeptoren am Gesamtpankreas, den Langerhansschen Inseln und Ratten-Insulinoma-Zellen (INS1).

Physiologische und molekularbiologische Untersuchungen erbrachten den Nachweis für einen Rezeptor-mediierten Einfluss des Pinealhormons Melatonin auf die Insulinsekretion pankreatischer β-Zellen. Melatonin führt zu einer Reduzierung der Insulinsekretion über die Senkung der Adenylatzyklase-cAMP-Transduktionskaskade und zur Förderung der Insulinfreisetzung über die Phospholipase C-IP3-Kaskade, wobei die Insulin-hemmende Wirkung des Melatonins, mediiert über den cAMP-Weg, überwiegt. Darüber hinaus konnte zurückliegend die Existenz des MT1-Rezeptors – und kürzlich auch des MT2-Rezeptors – auf pankreatischen β-Zellen nachgewiesen werden.

Minipigs have become popular pets in recent years. Therefore, an increasing number of veterinarians are being challenged by specific problems of these animals. This retrospective study gives an overview on the diagnoses and therapeutic interventions of the patients submitted to the clinic for swine at the University of Veterinary Medicine Vienna during the last 6 years (n=48). Most frequently, colic symptoms of the gastro-intestinal tract (n=12) and orthopaedic locomotion disorders (n=10), mainly due to accidents or long claws, could be observed, followed by urogenital tract and skin disorders (n=4 each). Therapeutic interventions are discussed with regard to medical aspects as well as statutory provisions.

This case report is the first description of a fibroepithelial hamartoma in a pig. The dysplasia, which covered half of the face of the newborn piglet, did not increase in relative size until the animal was euthanatized at 6 months of age. Histologic examination revealed a moderate orthokeratotic hyperkeratosis with variable degrees of epithelial proliferation. The main body of the dysplasia consisted of collagenous fibers. In addition, some proliferating small blood vessels as well as focally gathered dilated apocrine glands were evident. Given morphologic and clinical features, the diagnosis of a hamartoma seemed to be justified.

A monolithic phased array for the transmission of ultrasound is described. Formed on a lithium niobate substrate, it emits steered longitudinal waves and is intended for the contact testing of steel at 5 MHz. A simple model of the single element source is proposed which assures that the element acts as a localized normal force on the surface of the steel. Experimental measurements were made on the radiated waves from actual sources to determine the nature of this force. By extending the model to a group of such elements, predictions on the performance of a phased array can be made. These results show that a monolithic transmission array has useful properties for NDT.